This under-rated gem from Persona 1 is what comes to mind~
I definitely love the Magneto boss theme from "X-Men 2: Clone Wars" on the Sega Genesis/MegaDrive:
The only suckish part was the vocals kicked in when his shields were gone :/ and his health wasn’t bigger either.
Edited with better and official version.
A fantastic track in its own right, its reserved for boss fights with emotional weight for the MCs, and only plays a couple times throughout the initial trilogy of the story. So its meant to be an equally tense and emotional piece and I feel it does it well.